(I) Field of the Invention
The present invention relates to the field of processes for the preparation and delivery of ozonated water to at least one user point. The ozonated water may, as is known, be used in a large number of industrial applications: for example in connection with the environment (water treatment, etc.), for treating food products with ozone (washing food products such as seafood but also fruits and vegetables, etc. with ozonated water), or else in aquiculture and pisciculture (farms where ozone treatment of all or part of the water which supplies the spawning pool or pools of the user site is carried out.
(II) Description of the Related Art
Essentially, two types of processes for the preparation and delivery of ozonated water are known: a first type of process in which the in-line ozonation of the whole flow of water is carried out, and a second type of process in which ozonation of only a part of the flow of water is carried out in a bypass loop.
In both cases, it should be clearly noted that the key objective of this related art is to achieve a sufficient contact time between the ozone and the water, in order to obtain satisfactory disinfection of the water and proper management of the residual ozone and secondary oxidants content in the water thus treated.
The following comments can therefore be made regarding these two types of existing processes:
first, xe2x80x9cin-linexe2x80x9d type of process: In this case, the ozone is injected into a dissolution component such as a static mixer, which is placed in line on the pipe for the water to be treated for the user site. The necessary contact time (for disinfection) is then obtained either in an intermediate storage tank, or else quite simply over the length of pipe for the user site if its length is sufficient.
The required treatment rate (number of grams of ozone per m3 of water) is then controlled using the flow rate of water which is drawn downstream by the user site. Moreover, the ozonated-gas flow rate is generally fixed (a variable gas flow rate being very expensive to achieve).
second, xe2x80x9cozonation in a bypassxe2x80x9d type of process: In this second case, a fixed part of the flow of water of the user site is diverted in order to be ozonated.
A pump takes off a fixed flow of water, into which the ozone is injected by a dissolution component typically of the hydroinjector (venturi effect) type which is placed in the bypass. In this configuration it would be equally possible to use a static mixer but the hydroinjector is a less expensive item of equipment.
It is known that the hydroinjector only withstands very small variations in flow (the flow diverted is fixed for this reason). This is because if the water flowing through the hydroinjector varied substantially, this would lead to a variation in the flow of sprayed ozonate gas and therefore to a variation in the dissolved ozone content and therefore in the rate of treatment obtained.
As in the previous case, the required treatment rate (number of grams of ozone per m3 of water) can only be controlled on the basis of the flow of water drawn downstream by the user site, which does not provide any independence with regard to the parameters of the downstream user site.
These existing processes are therefore directly dependent on the parameters of the final application of the ozonated water, and are therefore difficult to adapt to applications which require large variations in treatment rate (depending, for example, on the products treated), in the flow of water, or else to incessant start/stop cycles which depend on the production pauses and shutdowns of the final application of the ozonated water.
One of the objectives of the present invention is therefore to provide a solution to the above-mentioned technical problems, by proposing a process which is capable of being adapted to requirements (rate, flow, etc.) of the final user application, while being controlled independently of the parameters of this final application.
The present invention therefore relates to a process for the preparation and delivery of ozonated water to at least one user point, according to which:
a) a storage buffer tank is provided for the ozonated water;
b) an upstream ozonation loop is provided, making it possible to supply the tank with ozonated water, for which:
the tank is integrated into the loop;
the upstream ozonation loop comprises a gas/liquid transfer component and a component for controlling the flow of water flowing in the loop;
an ozonated gas supply line is provided, linked by its downstream part to the transfer component and by its upstream part to an ozonator;
a fresh-water supply line is provided, connected by its downstream part to the upstream ozonation loop and fitted with a component for interrupting the fresh-water flow;
the loop portion located between the tank and the connection point of the fresh-water supply line is fitted with a component for interrupting the recirculation flow upstream of the tank;
c) a line is provided for feeding the at least one user point with ozonated water from the tank;
d) the tank fill level is controlled between a low level Nl and a high level Nh using the component for controlling the flow of water flowing in the ozonation loop, one or the other of the component for interrupting the fresh-water input and the component for interrupting the recirculation flow upstream of the tank being always open while the other of the components is closed.
The process according to the invention may also adopt one or several of the following characteristics:
during phases of ozonated-water consumption by at least one of the user stations, the component for interrupting the recirculation flow upstream of the tank is in the closed position, and the component for interrupting the fresh-water input is in the open position in order to allow fresh water to be admitted into the upstream ozonation loop, to be ozonated by the transfer component and to allow the tank to be fed with water ozonated in this way, the tank fill level being controlled, between the low level Nl and the high level Nh using the component for controlling the flow of water flowing in the ozonation loop, the basis of one of the following signals:
i) a measurement of the tank fill level,
ii) a measurement of ozonated water consumption by the consuming user station or stations;
during shutdowns or pauses in ozonated-water consumption by the at least one user station, the flow of ozonated water originating from the tank is recirculated toward this tank, before the flow of water reaches the user station;
during shutdowns or pauses in ozonated-water consumption by the at least one user station, the following measures are taken: as soon as the tank fill level goes above the high level Nh, the component for interrupting the fresh-water input is put into the closed position in order to interrupt the inflow of fresh water, and the component for interrupting the recirculation flow upstream of the tank is put into the open position in order to allow the ozonated water in the tank to be recirculated in the upstream ozonation loop thus closed;
during such shutdowns or pauses in consumption, the ozonator output is reduced to a minimum, non-zero output.
The invention also relates to a plant for the preparation and delivery of ozonated water to at least one user point, which comprises:
a) a storage buffer tank for ozonated water;
b) an upstream ozonation loop making it possible to feed the tank with ozonated water, for which:
the tank is integrated into the loop;
the upstream ozonation loop comprises a gas/liquid transfer component and a component for controlling the flow of water flowing in the loop;
an ozonated-gas supply line is provided, linked by its downstream part to the transfer component and by its upstream part to an ozonator;
a fresh-water supply line is provided, connected by its downstream part to the upstream ozonation loop and fitted with a component for interrupting the flow of fresh water;
the portion of loop located between the tank and the connection point of the fresh-water supply line is fitted with a component for interrupting the recirculation flow upstream of the tank;
c) a line for feeding the at least one user point with ozonated water, from the tank;
one or other of the component for interrupting the fresh-water input and the component for interrupting the recirculation flow upstream of the tank being always in the open position while the other of the component is then in the closed position.
According to one of the embodiments of the invention, the feed line of the user station or stations is fitted with a pumping component and with a tap, capable of turning the flow of ozonated water originating from the tank back toward this tank, before the flow of water reaches the user station.
According to one of the aspects of the invention, the plant comprises a data acquisition and processing unit, capable, during phases of ozonated-water consumption by at least one of the user stations:
of placing the component for interrupting the recirculation flow upstream of the tank, into the closed position, and of placing the component for interrupting the fresh-water input into the open position;
of acquiring one of the follwoing signals: a measurement of the tank fill level or a measurement of ozonated-water consumption by the consuming user station ro station;
of controlling, on the basis of one of the above two signals, the tank fill level between a low level Nl and a high level Nh.
The data acquisition and processing unit is advantageously capable, during shutdowns or pauses in ozonated-water consumption by the user station or stations, of putting the component for interrupting the fresh-water input into the closed position in order to interrupt the inflow of fresh water, and of putting the component for interrupting the recirculation flow upstream of the tank into the open position in order to allow the ozonated water in the tank to be recirculated in the upstream ozonation loop thus closed.
The data acquisition and processing unit is also advantageously capable, during such shutdowns or pauses in consumption, of reducing the ozonator output to a minimum output which is nonzero.
Other characteristics and advantages of the invention will emerge from the following description, given solely by way of illustration and in no way implying any limitation, and made with reference to the appended drawings.